1. Field of the Invention
The present invention is related to a distributive cache accessing device and method and more particularly, to a device and method capable of solving a traffic jam over the server side arising from simultaneous boot-up of a large number of diskless computers over the client side, and thus reducing the booting time of diskless computers.
2. Description of the Related Art
U.S. Patent Publication No. US20040153694 “Reliability of Diskless Network Bootable Computers Using Non-Volatile Memory Cache” discloses that computers over the client side temporarily store data transmitted from a remote boot server in a non-volatile memory cache (NVM). The data can then be retrieved from the NVM cache to resume operation when the network is unavailable or slow. The cache is later synchronized with the remote boot server when network conditions improve, so that network-bootable computers have higher reliability. The data stored in the NVM cache can be also used for cold booting. However, the data must be obtained from the remote boot server before storing them to the NVM cache and is not directly accessible from other nodes of the network to achieve a load-sharing mechanism.
U.S. Patent Publication No. US20050281280 “Method and System for Supporting Hardware Acceleration for iSCSI (Internet Small Computer System Interface) Read and Write Operations and iSCSI Chimney” discloses that the iSCSI read and write operations are performed via a TCP offload engine. The mechanism pre-registers certain hardware buffers. When receiving an iSCSI command, an iSCSI initiator first analyzes its packet information and compares them with the content of the pre-registered buffers. Data can then be transmitted or zero copied from the pre-registered buffers to the iSCSI initiator. The so-called zero copy concept is when users transmit data out via network sockets, and the system copies data to a kernel buffer and then allocates the content in the kernel buffer to a user buffer. Such allocation is done by a CPU. The kernel then allocates the content of the user buffer to the socket buffer of the kernel and makes the content accessible to communication protocol engines. Such method accesses cache data through shared memory, occupies less CPU resource and memory, and enhances the performance of the read and write operations of the iSCSI initiator. However, the cache data fails to be acquired from external nodes, and thus fails to distribute network traffic and work load to external nodes to improve performance.
Taiwanese Patent Publication No. 200913622 “WAN-booting System Enhancing Booting Efficiency of Diskless Computers” discloses that an iSCSI target won't execute access disks in accordance with iSCSI commands issued by each iSCSI initiator, but compares existing data in cache memory of the iSCSI Target. If identical data is found, one disk-accessing time can be saved to enhance performance. Such method is an extension of the conventional cache accessing mechanism, and its operation concept is also similar. However, such method fails to solve the network overhead incurred in the case of unavailable accessing cache, e.g. network traffic of iSCSI target.
In sum, the read and write operations in U.S. Patent Publication No. US20040153694 rely on the iSCSI target. Thus, the load of the iSCSI target increases and fails to distribute the load of the iSCSI target to each iSCSI initiator when a large number of iSCSI initiators simultaneously request for data. By reducing the data-accessing frequency in each buffer, U.S. Patent Publication No. US20050281280 enhances the operation efficiency of the iSCSI initiators. Taiwanese patent Patent Publication No. 200913622 reduces the disk-accessing frequency by comparing the cache data in the iSCSI target to raise the operating efficiency of the iSCSI initiators. However, the issue of consuming the network bandwidth of the iSCSI target still remains. To reduce network traffic of the iSCSI target and enhance remote booting and operating performance of network diskless computers, conventional techniques can be further refined.